A polarity-reversal protector of this type can, in principle, be used in connection with power sources for greatly varying applications. The mode of operation and advantages of such a polarity-reversal protector are explained in the following on the basis of the example of a power source used in motor vehicle technology, specifically an automobile battery and/or a power source which temporarily replaces the automobile battery. The automobile battery is typically only installed and connected to the vehicle electrical system directly before the motor vehicle is put into operation, so that it can supply multiple consumers with power and is also recharged again and again via a generator, the dynamo. During the vehicle manufacturing, the vehicle testing, and even during transport, an external power source, which then temporarily fulfills the function of the automobile battery, is connected to the vehicle electrical system only if necessary. However, even after a motor vehicle is put into operation, it can be necessary to bypass the automobile battery temporarily using an external power source, when a starting aid is used, for example.
In all of these cases, the poles of the particular power source to be connected are transposed again and again in practice, which is referred to as polarity reversal. Overheating of parts of the generator and even destruction of the generator, for example, can occur in this case. In addition, surrounding systems of the vehicle electrical system can be destroyed by the local generation of heat. Overall, polarity reversal represents a danger for the safety of all connected systems and also of the power source itself.